1. The Field of the Invention
The present invention relates generally to webs and films. Specifically, the invention relates to methods of creating a stock roll including a folded film or web within another folded film or web.
2. Background and Relevant Art
Thermoplastic films are a common component in various commercial and consumer products. For example, grocery bags, trash bags, sacks, and packaging materials are products that are commonly made from thermoplastic films. Additionally, feminine hygiene products, baby diapers, adult incontinence products, and many other products include thermoplastic films to one extent or another.
Thermoplastic films have a variety of different strength parameters that manufacturers of products incorporating a thermoplastic film component may attempt to manipulate to ensure that the film is suitable for use its intended use. For example, manufacturers may attempt to increase or otherwise control the tensile strength of a thermoplastic film. The tensile strength of a thermoplastic film is the maximum stress that a film can withstand while being stretched before it fails. Another strength parameter that manufacturers may want to increase or otherwise control is tear resistance. The tear resistance of a thermoplastic film is the amount of force required to propagate or enlarge a tear that has already been created in a film. Still further, a manufacturer may want to increase or otherwise control a film's impact resistance.
When forming various products from thermoplastic films, a manufacturer may fold the thermoplastic film in half (or otherwise create a folded film) and use the folded film to produce a product. For example, the manufacturer may use a folded film to create a bag. In particular, the manufacturer may seal the sides of the folded film adjacent the fold. The sealed sides and the bottom fold may form the three joined sides of a bag.
Recent developments in bag technology have discovered that bags having a bag-in-bag construction can provide many advantages over conventional bags. To form such bag-in-bag products it is often desirable run a first film folded nested within a second folded film through a bag-making machine. The machine can seal the sides of the folded films adjacent the folds to form a doubled-layered bag.
Unfortunately, conventional methods for combining folded films have various disadvantages that lead to undesirable conditions. For example, conventional methods for combining folded films may require significant machine width to handle wide webs and machine direction length to fold the films. Furthermore, conventional methods for combining folded films may lead to web handling and wrinkle issues that are undesirable. In addition to the foregoing, it may be necessary to redesign or significantly modify existing manufacturing processes and machinery by adding additional stations for folding and inserting the second film within the first film. Due to space and cost constraints, this is often undesirable or impractical.
Accordingly, there are a number of considerations to be made in thermoplastic films and manufacturing methods.